The Food & Drug Administration's Center for Veterinary Medicine (CVM) has issued a new guidance for industry (GFI) for public comment: GFI #264 "Standardized Medicated Feed Assay Limits February 2020."

CVM said it establishes assay limits for drugs in medicated feeds (Type B and Type C medicated feeds) as part of the approval process for Type A medicated articles. The term “assay limits” refers to how much the measured amount of drug can deviate from the labeled amount of drug. The assay limits for Type B and Type C medicated feeds are specified as a range and published in 21 CFR §558.4(d).

When a medicated feed assay value falls within this range using a validated method accepted by CVM, it indicates that the measured drug level in medicated feed is consistent with the labeled drug level, CVM said, noting that the assay limits are not intended to permit a feed manufacturer to add more or less than the labeled amount of drug to the medicated feed.

According to CVM, assay limits are used pre-approval to ensure that medicated feeds in Target Animal Safety (TAS), Effectiveness (EFF), Chemistry, Manufacturing & Controls (CMC), Bioequivalence (BE) and Human Food Safety (HFS) residue chemistry studies contain the appropriate amount of drug, and they are used post-approval for compliance and customer service purposes.

The new GFI #264 recommends a standardized set of assay limits for medicated feeds, CVM said, explaining that standardized medicated feed assay limits allow for predictability in the review process as sponsors can determine early in the drug development process what assay limits they should expect to meet for medicated feeds used in TAS, EFF, CMC and HFS residue chemistry studies.

The draft guidance document can be downloaded here, and the accompanying Federal Register notice can be read here.

Comments may be submitted online by April 27 and should be identified with Docket Number FDA-2019-D-5664.